Will someone please contact the flex hone company and ask them what they think. Is their process the same as or equivalent to the silicone paste step. I would like someone else to do this to help verify what I have said, in other words it would not add much to this thread if I were to do it myself. Also another set of eyes would show a new angle or point of view to the same problem and consequently add much to the discussion.

I can contact someone who may have enough sway with Sunnin to add directly to this topic. I will try and see what happens.

Hmmm, that's an interesting view. The shop that i have "redoing" my ausils said that the main reason to do this is to be sure the new rings "bite" in and seal properly. Otherwise it's a big risk that the new rings with an un cross hatched wall may never seal right.

reply from sunnin
 

I received a reply from Sunnin and they sent over a pdf of their process but it is very similar to the KS doc. I specified that we were interested in the air-cooled engines and this is what they sent. I am replying and asking them to verify that the process is the same for us. The bottom line is this, the final polishing or lapping process consists of felt pads instead of stones and silicon grease. There is no crosshatch after, only a "dull matte finish"

Crosshatch is not required as the lapping process exposes silicon particles in the cylinder wall. It doesn't cut grooves into the wall but removes aluminum from between the silicon particles.

The board won't let me upload a PDF, if anyone wants the file PM me with an email address.

Any process with a sunnin hone would should leave a cross hatch pattern. Honing stones have randomly placed grit, silicone pasete is also random "grit". THe cross hatch pattern is due to the up and down action of the honing machine, along with the rotating, cutting material. The question is the roughness of the cross hatch. It may end up so fine that it is difficult to see with the naked eye.

To make perfactly ROUND cylinders. Some kind of pattern MUST result from the process used. I cannot think of one that does not. Even the rings are lapped (at least the good ones), and if you look close enough you can see a pattern on them. The rings may have a final protective coating that could obscure the pattern, but its sort of like cosmolene, non functional, except for the rust protection.

Even if the silicone paste only picks off Al and not Si, there should be a pattern, due to the machineing process used, ie it is not a randomized process, like an orbital sander. but a periodic one, consequently a periodic pattern, ie a cross hatch. I suspect that a paste would result in a less well defined pattern, due to the lack of anything holding the grit in position for any period of time. I suspect that this could acutally work against optimal lubrication, as the well defined groves hold oil very well and have been proven to work extreemly well in protecting an engine from wear. The groves provide for a for a flow of clean oil and a means for removal of debre from the cylinder walls. But in thinking about this some more, the grit will establish its own "flow" pattern, which could indeed be optimal for oil as well. Again this pattern MUST be a cross hatch at a macroscopic level. WHY? the periodic machining.

So, avoiding symatics, it is the cross hatch pattern that is responsible for oiling, on the macroscopic level, on the microscopic level it may well be the microscopic voids, but again the voids are arranged in a cross hatch pattern due to manufacturing methods. Or at least thats the way I think it works. Any other ideas???

Here's a pic of my 80k mile bores, cross-hatch pattern clearly visible...

http://forums.pelicanparts.com/uploa...1072336568.jpg


I'll check about the reasons for all this (cross hatch)when I return to work after the hols. I work with the guys who are responsible for the spec. of all Federal Mogul (Goetze etc) cylinder components ie pistons, rings and liners. They are the leading European authorities on this sort of stuff.....

The appearance of a cross hatch pattern in the alusils is just the effect of the honing machine, it's not the same as with ferrous cylinders. If you could see the surface in enough detail you could see the CH is only in the aluminum. According to the engineers I've heard from the importance is in the removal of aluminum from between the silicon particles.

Any new updates...this thread sorta withered on the vine. I was especially curious to hear from Nathan M about what he decided to go with..
R/
Dustin

Here's an interesting article from 1999:

http://waw.wardsauto.com/ar/auto_boring_trutheverybodys_ideas/index.htm

Rondinone,
Wow that is interesting. The passage on Alusil almost totally opposes what most believe about why Porsche went with Alusil in the first place i.e. as a cost saving measure:

"Again, however, there are considerable problems. Alusil blocks must be made in a slow, low-pressure process, says Mr. Sach, and the original alloy itself is more expensive. He believes Alusil is good for low-volume use where cost and manufacturing speed are not the priorities.

Alusil's cost might be bearable even for mainstream vehicles, but a foreign automaker engineer insists, "Throughput time is not acceptable for high-volume lines. We would never consider this process."

Perhaps Porsche decided to switch to Alusil in an attempt to capitalize on the technology, and found it was TOO expensive, which prompted the switch back to Nikasil? Perhaps the scare of high sulphur content fuels in the US prompted the change to Alusil? All speculation of course, but it would be interesting to hear from Porsche on this matter. the change to Alusil?
Again the significance of this article is the implication that most of the folklore and urban myths surrounding the use Alusil (eg cost, durability etc) don't seem to jive with the reality of Alusil as a process. Actually to tell you the truth, I'm kinda hoping to find Alusil cyls when it comes time to re-build. If nothing else, at least I'm a bit more educated on the subject and less likely to follow the herd on the whole "Alusil cyls are throw-away" items.

R/
Dustin

In a separate thread the question of using JEs in Alusil cyls came up and no one seemed to have a definitive answer but here's a quote from the "Power for CIS 911s" page "you can get a respectable power increase (especially in torque) by bumping compression up to 9.5:1, or even 9.8:1 if you won’t have to pull into West coast gas stations and use their “premium” 91 octane fuel. JE Pistons sells the appropriate piston sets (that include Goetze rings, wrist pins, and clips) for under $1,000, and roughly speaking, you get about a 10 percent power increase per compression point increase. The only caveat about the piston swap is that JE pistons won’t work with Alusil cylinders—but those cylinders were rarely used on CIS cars."

Full article is here: http://www.pelicanparts.com/techarticles/911_engine_rebuild/911_engine_rebuild2.htm

anh911,
I read that too. Seems to me that a lot of CS cars used Alusils; evident by the very existence of this thread. From what I gather the iron coating on the pistons of the Alusil assemblies was to protect the soft, aluminum piston from wearing out against the silicon matrix. I think if stright JE's went into a Alulsil cyl,they'd be worn to a nub very quickly...?
R/
Dustin

Not sure how long it would take but yes, they would wear rapidly and ruin the finish on the cylinders as well.

I'd be interested to hear from anyone at JE about it. I remember a guy beadblasting a set of pistons from a 2.7 with KS liners and you could see where it had blasted the coating off. He was not a happy camper when he found out they had to be replaced.

anh911,

I converted the pdf to jpeg so the board can see it. This is just what we needed.

http://forums.pelicanparts.com/uploa...1072828944.jpg

http://forums.pelicanparts.com/uploa...1072828965.jpg

You can see that they call for the Sunnen silicon compound AN-30, which according to their current catalog should be available:

http://www.sunnen.com/product/pdf/79b-87.pdf

Page 82 (4).

I'm not sure if the entire honing process would be necessary, as in the case of a vega overheat. Based on the experiences of people who have had successes without honing, such as superman, we could probably get by with just the final conditioning. Let's hear some opinions on this.

I'm not sure if I'll ever be happy about finding alusils, but if we can get to the point where it's not the end of the world to have them, then I'll be satisfied.

If you go to the KS website and read about their aluminum technology, they describe the Cayenne block manufacturing. If alusil was sooooo bad, why would Porsche, Honda, BMW and Mercedes use it now?

It's time for an alusil revolution.http://www.pelicanparts.com/support/smileys/2ar15.gif Long live the SC/Alusil/WDP!

By the way, a few more views and we'll have a more popular thread than Wayne's disclaimer.

Count me in for the revolution but hang on - don't forget us 3.2 guys!!

The next one to alusil bash get's it http://www.pelicanparts.com/support/smileys/spankA.gif

Viva alusil! http://www.pelicanparts.com/support/smileys/ar15.gif

I just finsihed honing a chevy V8 block that I had bored from 3.75" to 3.997" and finished honed to 4.0000" to 4.0005" using the CK-10 honing machine and almost identical stones and settings. The final step was done using a splash of honing oil and a hand drill using 180 girt silicone carbide flex hone for about one minute at 300 RPM and one stroke per second. Exactly the same step I used on the Porsche cylinders for conditioning, but without the preceeding steps that removed metal.

Does that add to anyones comfort level??

Well, I'm a Porsche wrench, so I'll speak up.

Honing with the "grape hone" is acceptable to restore a crosshatch pattern on Nikisil cylinders ONLY- 4 or 5 light passes with a well lubricated hone are all that is necessary. If there is a visible crosshatch pattern, this procedure is unnecessary.

Reapplying the paste is NOT necessary unless the cylinder needs to be honed due to the cylinder being out of specification.

The paste actually applies deposits the silicon into the aluminum

Honing an alusil cylinder without applying the paste will destroy the P&C

Piston rings may be replaced provided that the cylinder meets all criterea listed above. Have done several in the past, many have been going for more than 10 years. The real trick in getting the rings to seat is using regular dinosaur oil for the first 1000 miles, then switching to synthetic.

Yes I have access to a Sunnen machine and the appropriate tooling\paste etc.

Can post exerpts from 944 workshop manual if there is interest. 944\968 use nothing but alusil cylinders, so the honing procedure\criterea is explained in great detail.

AFJuvat

Thank you, that would be appreciated.
Then we can dismiss all the misinformation re "grape hones" etc., etc.

I have a spare set of in-spec Alusils that I was going to have Nikasil plated. If I can re & re them as you describe, it should cost a lot less.

Since neither the grape style hone or the silicone paste remove any metal the exact ammount of honing is not real critical. 4 or 5 light passes ( the pressure is not adjustable with grape hones) vs 30 seconds or even one minute, in other words just enough to restore the finish so the new rings will seat. With the sunnin hone the pressure is adjustable and the mfg recommendations should be followed.

AFJuvat,
Although I would never argue with a guy who makes is living out of this business, I do have a quick comment/question based on your comment:

"The paste actually applies deposits the silicon into the aluminum"

From what I have researched, the silicon particles are disprersed throughout the aluminum substrate during the casting of the cylinder itself. The silicon paste in the final polishing of the procedure removes any of the bent or folded aluminum material from the boring process (on a micorscopic level), exposing the new layer of silicon particles. My question is, how can a paste apllied at relatively low pressure via felt pads re-apply silicon particles to the surface of the cyl that would be of any significance? I would have to think that any of the paste material left behind including the silicon particles would be removed during the final cleaning of the cylinder. Using a very simple analogy, it seems to me that the silicon paste cleans the bore in the same manner toothpaste cleans teeth...simply removes the upper layer of crap via a very slight mechanical action of embedded "grit" whether it be silicon particles or something else to expose the fresh surface...
R/
Dustin

R/
Dustin

""The paste actually applies deposits the silicon into the aluminum"

I'm not a metallurgist, but I wondered about that too. Perhaps AFJ meant something else.
Regardless, please let's see those docs on Alusil re & re from the 944 manuals.